Quantum-Amplified Simultaneous Quantum-Classical Communications

TL;DR

This paper demonstrates how to integrate quantum communication elements into classical free-space optical systems with minimal modifications, enhancing overall throughput through quantum amplifiers at the receiver.

Contribution

It introduces a method to add quantum communication capabilities to classical FSO systems using Gaussian displacements and quantum amplifiers, with detailed analysis of the minimal signal requirements and receiver modifications.

Findings

Quantum amplifiers can boost combined classical-quantum throughput.

Minimal infrastructure changes enable quantum-classical coexistence.

Additional receiver components improve quantum communication performance.

Abstract

Classical free-space optical (FSO) communication promises massive data throughput rates relative to traditional wireless technologies - an attractive outcome now being pursued in the context of satellite-ground, inter-satellite and deep-space communications. The question we investigate here is: how can we minimally alter classical FSO systems, both in infrastructure and in energy input, to provide some element of quantum communication coexisting with classical communications? To address this question, we explore additional Gaussian displacements to classical FSO encoding on the satellite, determining the minimum signal requirements that will meet given specifications on the combined classical and quantum communications throughput. We then investigate whether enhanced quantum-based amplifiers embedded in receivers, which have proven advantageous in standalone quantum communication, can enhance our combined classical-quantum communication throughput. We show how this is indeed the case, but only at the cost of some additional receiver complexity, relative to standalone quantum communications. This additional complexity takes the form of an additional beamsplitter and two heterodyne detectors at the receiver. Our results illustrate a viable pathway to realising quantum communication from classical FSO systems with minimal design changes.